Short seller Andrew Left says he's found a 'business dirtier than Herbalife'

Andrew Left is back at it again.

The Citron Research founder tweeted on Wednesday that Canadian e-commerce company Shopify is a "business dirtier than Herbalife."

He also posted a seven-minute YouTube video outlining his bear case, entitled "Citron Exposes the Dark Side of Shopify - The FTC Will Take Notice," and posted a report to his firm's website.

In the video, Left lays out the big question he has around the company: Outside of the roughly 50,000 verifiable merchants working with Shopify, who are the other 450,000 the company says it has? Many of them are, among other things, influencers paid to promote the company, according to Left.

"The company has mastered the good ol' get-rich-quick scheme," says Left in the video. "What's never discussed on why Wall Street is the real business behind Shopify."

Left placed a price target of $60 on Shopify's stock, which is roughly 49% below the Tuesday's closing price. Meanwhile, Shopify's stock plunged as much as 10% to $105.02 on Wednesday.

And while the merits of Left's claims are certainly up for debate, Shopify's stock plunge proves once again that when Left speaks out against a company, the market listens.

Past targets of Left's have included Express Scripts, which he said in December could be targeted during the Trump administration, and The Chemours Co., a DuPont spin-off he warned might be bankrupted by a class-action lawsuit.

But Left is perhaps most well-known for his damning October 2015 report that accused Valeant Pharmaceuticals of being a "pharmaceutical Enron," and helped bring up questions regarding the firm's accounting and relationship with specialty pharmacy Philidor.

Read the full Citron Research report here